The efficacy of ciliary function in the developing lung has not been studied nor has the development of this function been studied during the perinatal period. The specific aims of the research are designed to provide information about the variability and status of ciliary activity in the developing lung of fetal puppies and neonatal guinea pigs. The long term objective is to clarify whether ciliary function in the fetal and postnatal period is different with respect to its ability to respond to stimuli which are presented to it when compared to the adult. An experimental model consisting of an intact, in vitro, whole lung preparation, with inflated airways bathed in a controlled extracellular fluid environment will be used for the study. The specimen can be studied after in vivo or in vitro exposure. By exposing airways to carefully controlled environmental manipulations of tracheal fluid pH, extracellular pH, temperature and oxygen concentrations the responses of ciliary activity will give an important indication of the capability of this mechanism during infancy. Should the responses to the above stimuli be less than those observed in control mature airways, then it can be inferred that ciliary function in an immature pulmonary epithelium may respond poorly to other noxious or particulate insults. This diminished response could be one of the factors predisposing to viral or bacterial colonization of the neonatal lung.